Blue is one of the seven colours into which the rays of light divide themselves when refracted through a glassprism, seen in nature in the clear expanse of the heavens; the term is also applied to a dye or pigment of this hue.
The substances used as blue pigments are of very different natures, and derived from various sources; they are all compound bodies, some being natural and others artificial. They are derived almost entirely from the vegetable and mineral kingdoms. The principal blues used in painting are ultramarine, which was originally prepared from lapis-lazuli or azure-stone - a mineral found in China and other oriental countries - but, as now prepared, it is an artificial compound of china-clay, carbonate of soda, sulphur, and charcoal; Prussian or Berlin blue, which is a compound of cyanogen and iron; blue bice, prepared from carbonate of copper; indigo blue, from the indigo plant. Besides these, there are numerous other blues used in art, as blue-verditer, smalt- and cobalt-blue, from cobalt, lacmus or litmus, etc.
Before the discovery of aniline or coal-tar colours dyers chiefly depended for their blues on woad, archil, indigo, and Prussian blue, but now a series of brilliant blues are obtained from coal-tar, possessing great tinctorial power and various degrees of durability.
Blue as a colour ranges from green-blue (turquoise) through to purple-blue (indigo).
Alice blue - A very light greenish-blue colour.
Aquamarine - A bluish-green colour.
Azure - A deep blue colour reminiscent of the sky.
Aquamarine - A pale greenish-blue colour.
Bice blue - A medium blue colour
Cambridge blue - A light blue colour.
Cobalt blue - A deep blue colour with a greenish-tint. The colour of old blue glass.
Chrome green is a composite pigment made by combining a small amount of Prussian blue with pale yellow chrome. Chrome green comes in various shades, all of which are opaque with good staining ability. Chrome green is fairly permanent, but tends to turn blue under the influence of weathering, and discolour upon contact with sulphur and alkalis. Chrome green darkens as it dries, making it a difficult pigment to colour match. Research Chrome Green
Congreves were a predecessor of the Lucifer matches. The splints were dipped in sulphur and then tipped with the chlorate of potash paste, in which gum was substituted for sugar, and there was added a small quantity of antimony sulphide. The match was ignited by drawing it through a fold of sandpaper under pressure. The matches were banned in France and Germany on account of being dangerous. Research Congreves
Engraving is the art of representing objects and depicting characters on metal, wood, precious stones, etc, by means of incisions made with instruments variously adapted to the substances operated upon and the description of work intended.
Impressions from metal plates are named engravings, prints, or plates those printed from wood being called indifferently wood engravings and wood-cuts. While, however, these impressions are not altogether dissimilar in appearance, the processes are distinct. In plates the lines intended to print are incised, and in order to take an impression the plate is daubed over with a thick ink which fills all the lines. The surface is then wiped perfectly clean, leaving only the incised lines filled with ink. A piece of damp paper is now laid on the face of the plate, and both are passed through the press, which causes the ink to pass from the plate to the paper. This operation needs to be repeated for every impression, for the wood block, on the contrary, the spaces between the lines of the drawing are cut out, leaving the lines standing up like type, the printing being from the inked surface of the raised lines, and effected much more rapidly than plate printing.
Engraving on wood, intended for printing or taking impressing from, long preceded engraving on metals. The art is of eastern origin, and at least as early as the 10th century engraving and printing from wood blocks was common in China. We first hear of wood engraving being cultivated in Europe by the Italians and Germans in the 13th century. For a hundred and fifty years, however, there is small indication of the practice of the art, which was at first confined to the production of block-books, playing cards, and religious prints. In the 15th century the art of printing from engraved plates was discovered in Florence by Maso Finiguerra.
Engraving had long been used as a means of decorating armour, metal vessels, etc, the engravers generally securing duplicates of their works before laying in the niello (a species of metallic enamel) by filling the lines with dark colour, and taking casts of them in sulphur. The discovery of the practicability of taking impressions upon paper led to engraving upon copper plates for the purpose of printing from.
The date of the earliest known niello proof upon paper is 1452. The work of the Florentine engravers, however, was almost at once surpassed in Venice and elsewhere in North Italy by Andrea Mantegna, Girolamo Mocetto, Giovanni Batista del Porto, and others. In Marc Antonio Raimondi, who wrought under the guidance of Raphael, and reproduced many of his works, the art reached its highest point of the earlier period, and Rome became the centre of a new school, which included Marco da Ravenna, Giulio Bonasone, and Agostino de Musis.
In the meantime, in Germany the progress of the art had been not less rapid. Of the oldest school the most important engraver is Martin Schongauer. He was, however, surpassed a generation later by Albert Durer who excelled both in copper and wood engraving, especially in the latter. Among his most famous contemporaries and successors were Burgkmair and Lucas Cranach. The Dutch and Flemish schools, of which Durer's contemporary Lucas van Leyden was the head, did much to enlarge the scope of the art, either by paying increased attention to the rendering of light and shade, and the expression of local colour, as in the case of Cornelius Cort and Bloemart; or by developing freedom and expression of line, as in the case of Goltzius and his pupils.
Rubens influenced engraving through the two Bolswerts, Vorstermann, Pontius, and de Jode, who engraved many of his works on a large size. Towards the end of the 17th century etching, which had before been rarely used, became more common, and was practised with great success by Rembrandt and other painters of that period. In France Noel Garnier founded a school of engraving about the middle of the 16th century; but it produced no work of any high distinction until the reign of Louis XIV, when Nanteuil's pupil Gerard Edelinck and Gerard Audran flourished. The former was skilled in using his graver to produce colour effects, the latter is famed for his engravings from Nicolas Poussin and Le Brun. But these were all surpassed about the middle of the 18th century by Wille, a German resident in Paris.
Before the middle of the 17th century England produced little noteworthy work, availing herself principally of the work of foreign engravers, of whom many took up temporary and even permanent residence. The first English engraver of marked importance was William Hogarth, whose works are distinguished for character and expression. Vivares, a Frenchman by birth, laid the foundation of the English school of landscape-engraving, which was still further developed by William Woollet, who was also an excellent engraver of the human figure.
In historical engraving a not less remarkable advance was made by Sir Robert Strange, and Richard Earlom produced some admirable works in mezzotint. In succession to these came William Sharp, James Bazire, Bartolozzi, James Heath, Bromley, Raimbach, and others.
The substitution of steel for copper plates around 1820 to 1830 gave the power of producing a much larger number of fine impressions, and opened new possibilities for highly-finished work.
During the closing years of the 18th century line engraving attained a depth of colour and fulness of tone in which earlier works generally are deficient, and during the following century it reached a perfectness of finish which it had not previously attained. A picture, whether figure or Landscuape, may be translated by line engraving with all its depth of colour, delicacy of tone, and effect of light and shade; the various textures, whether of naked flesh, silk, satin, woollen, or velvet, all successfully rendered by ingenious modes of laying the lines and combinations of lines of varying strength, width, and depth. Among engraverswho have produced historical works of large size and in the line manner the names of Raphael Mrghen, Longhi, Anderloni, Garavaglia, and Toschi, in Italy; of Forster, Henriquel-Dupont, Bridoux, and Blanchard, in France; of John Burnet, J H Robinson, Doo, J H Watt, and Lumb Stocks, in England, stand pre-eminent.
Among historical and portrait engravers in the stipple or dotted manner the names of H T Ryall, Henry Robinson, William Holl and Francis Holl, may well be mentioned.
In the period 1820 to 1860 landscape engraving attained a perfection in Great Britain which it had not attained in any other country, or at any other time. Among landscape engravers the names of George Gooke, William Miller, E Goodall, J Cousen, K Brandard, and William Forrest hold the foremost places. In mezzotinto engraving Samuel Cousins is unrivalled.
In the period 1830 to 1845 various publications called Annuals, composed of light literature in prose and verse, and illustrated by highly-finished engravings in steel, were very popular. The engravings were necessarily of small size, and are generally of great excellence. A number of them both figure and landscape are executed with such finish and completeness as to be esteemed perfect works. The unrivalled illustrations of Rogers' Poems and Rogers' Italy after Turner and Stothard belong to this period. Many of the originals of the engravings in the Annuals were finished pictures of large size.
A great part of the difficulty in engraving on a small scale from a large picture, consists in determining what details can be left out, and still preserve the full effect and character of the original. The most noted engravers for work of small size are Charles Heath, Charles Bolls, W Finden, E Finden, E. Portbury, J Goodyear, F Engleheart, Henry Le Keux, E Goodall, and W Miller.
After 1870 many plates were produced by a combination of etching and dry point, a comparatively cheap and rapid process. Such works were fashionable and very popular with collectors. But while some of them have been excellent of their kind, the process is of limited resource, and the best works in this manner will not stand comparison with the masterpieces of line engraving. Through lack of encouragement, change of fashion, and the adoption of other methods of reproduction such as photography, line engraving rapidly becoming a lost art in Great Britain. The men who made line engraving famous died, and there was no sufficient inducement for younger men to pursue that art. In France and in Germany some able line engravers were still in practice at the start of the 20th century.
Line Engraving, as implied by the term, is executed entirely in lines. The tools are few and simple. They consist of the graver or burin, the point, the scraper, and the burnisher; an oil-stone or hone, dividers, a parallel square, a magnifying lens; a bridge on which to rest the hand; a blind or shade of tissue paper, to make the light fall equally on the plate, callipers for levelling important erasures, a small steelanvil, a small pointed hammer, and punches. In etching, the following articles are required: a resinous mixture called etching-ground, capable, when spread very thinly over the plate, of resisting the action of the acids used; a dauber for laying the ground equally; a hand-vice; some hair-pencils of different sizes, and bordering wax, made of burgundy-pitch, bees'-wax, and a little oil.
In engraving, the plate, which is highly polished and must be free from all scratches, is first prepared by spreading over it a thin layer of ground. The surface is then smoked, and the outline of the picture transferred to it by pressure from the paper on which it has been drawn in fine outlines by a black-lead pencil. The picture is then drawn on the ground with the etching-needle, which removes the ground in every form produced by it, and leaves the bright metal exposed. A bank of wax is then put round the plate and diluted acid poured on it, which eats out the metal from the lines from which the ground has been removed, but leaves the rest of the plate untouched. The plate is then gone over with the graver, the etched lines clearly defuned, broken lines connected, new lines added, etc. Sometimes the plate is rebitten more than once, those parts which are sufficiently bitten in the first treatment being stopped with varnish, and only the selected parts exposed to after-biting. Finally the burnisher is brought into play alternately with the graver and point to give perfectness and finish.
Such is the process for landscape engraving. In historical and portrait engraving of the highest class, the lines are first drawn on the metal with a fine point and then cut in by the graver, first making a fine line and afterwards entering and re-entering till the desired width and depth of lines is attained. Much of the excellence of such engravings depends on the mode in which the lines are laid, their relative thickness, and the manner in which they cross each other. In historical engraving etching is but little used, and then only for accessories and the less important parts.
In Soft-ground Etching the ground, made by mixing lard with common etching-ground, is laid on the plate and smoked as before, but its extreme softness renders it very liable to injury. The outline of the subject is drawn on a piece of rough paper larger than the plate. The paper is then damped, and laid gently over the ground face upwards, and the margins folded over and pasted down on the back of the plate. When the paper is dry and tightly stretched the bridge is laid across, and with a hardish pencil and firm pressure the drawing is completed in the usual manner. The pressure makes the ground adhere to the back of the paper at all parts touched by the pencil, and on. the paper being lifted carefully off, these parts of the ground are lifted with it, and the corresponding parts of the plate thus left bare are exposed to the subsequent action of the acid. The granulated surface of the paper, causing similar granulations in the touches on the ground, gives the character of a chalk-drawing. The biting-in is effected in the same manner as already described, and the subject is finished by re-biting and dotting with the graver.
Stipple, or Chalk Engraving, in its pure state, is exclusively composed of dots, varying in size and form as the nature of the subject demands, but few stipple plates are now produced without a large admixture of line in all parts, flesh excepted. A great advance, however, was made in stipple engraving by the introduction of large and varied forms of dotting in the draperies, the results almost rivalling line engraving in richness and power.
The Mixed Style is based on mezzotinto, which, still forming the great mass of shading, is in this method combined with etching in the darker, and stipple in the more delicate parts. By this combination a plate will produce a larger number of good impressions than were it done entirely in mezzotinto.
The wood best adapted for engraving is box. It is cut across the grain in thicknesses equal to the height of type, these slices being subjected to a lengthened process of seasoning, and then smoothed for use. Every wood engraving is the representative of a finished drawing previously made on the block; the unshaded parts being cut away, and the lines giving form, shading, texture, etc, left standing in relief by excavations of varied size and character, made between them by gravers of different forms. Drawings on wood are made either with black-lead pencil alone or with pencil and indian ink, the latter being employed for the broader and darker masses. It is now much the practice to photograph drawings made in black and white upon the wood instead of making the drawing on the wood block. When the drawing is put on the wood by washes or by photography instead of being entirely done by pencil lines, the engraver has to devise the width and style of lines to be employed instead of cutting in facsimile, as is the case when the drawing is made entirely in lines. The tools required for wood engraving are similar but more numerous than those of the engraver on copper or steel. Research Engraving
Fumigation is the application of fumes, gas, or vapour for the purpose of disinfecting houses, clothes, and the like. The fumes of heated vinegar, burning sulphur, or the like, formerly employed, are of little value. Research Fumigation
In its narrow, everyday use, vegetable is a word indicating any herb that is cultivated specially for table use in whole or part, such as the turnip (root), cabbage (leaves), broccoli (flowers), peas and beans (fruit). In its widest sense it includes all living things that are not animals - trees, shrubs, herbs, ferns, mosses, seaweeds, fungi, and the microscopic diatoms.
The unit of structure, the cell, is essentially the same in both animals and plants, but the combination of the cells into tissues and organs shows marked differences.
All animals depend for their food upon material originally elaborated by plants. The green plants alone have the power to construct this basic food material from elemental substances, and physiological processes different from those of animal assimilation are rendered necessary. The fungi approach the animals in this respect: they must feed upon material that has already done service as part of the structure of other plants or of animals.
The fine divisions of roots explore the soil in search of water in which are dissolved the salts of sodium, iron, potassium, phosphorus, calcium, sulphur, etc. The hairs with which the rootlets are clothed absorb this fluid by osmosis, and it is passed upward through the long vessels of the wood bundles until it reaches the cells of the leaf. These cells contain green bodies (chloroplasts) in their protoplasm, and it is these that impart the green colour to leaves and soft shoots. In the leaf-skin (epidermis) there are innumerable pores or stomata through which surplus water from the roots is evaporated and through which atmospheric air is admitted to the spaces between the leaf-cells.
The chloroplasts in these cells have the power to utilise solar energy in decomposing the carbon dioxide of the air, and the cells retain the carbon, setting free the oxygen. Water from the roots is broken up also into its elements, hydrogen and oxygen, and with these plus carbonstarch is formed. This, converted into grape sugar, is passed from cell to cell to parts of the plant whore it is needed for the production of new cells, wood, bark, leaves, or fruit. Starch is the material from which are made all the organic substances produced by the plant.
The surplus over present requirements is stored up as reserves in seeds, enlarged roots or stems, bulbs, or tubers for renewed growth or floral display at a later season. Waste products are converted into resins, oils/wax, or alkaloids - many of these being of considerable economic value to man. Part of the water stream from the roots passes by osmosis from cell to cell, where it is necessary in order to keep the protoplasm in an active condition; any insufficiency is followed by a flagging of the tissues, the drooping of leaves and young shoots. In addition to the absorption of carbon by the protoplasts for building purposes, the leaf-cells also take up oxygen from the atmosphere and give off carbon much as animals do.
As the plant respires without lungs and assimilates without digestive organs, so also it can effect movements without a muscular system and react to external stimuli without a nervous system. It is sensitive to light and heat; many plants have distinct night and day positions for their leaves. It responds positively and negatively to the force of gravity, the root going down into the earth and the stem rising into the air. The growing tip of a stem or shoot commonly nutates, i.e. moves from side to side or in a circle or ellipse. The plant can orientate itself, i.e. take up a definite position in regard to the incidence of light or other external stimulus. These movements appear to be controlled largely by alterations in the position of the mobile chloroplasts.
The reproductive process is, in essentials, similar to that of animals, the ovules or seed-eggs in the ovary requiring to be fertilised by male sperms represented by the pollen grains produced in the anthers. The result of such fertilisation is to cause the ovule to develop into an embryo capable of further development under suitable conditions into a plant resembling the parent. Research Vegetable
An apiary is a placefor keeping bees. The apiary should be well sheltered from strong winds, moisture, and the extremes of heat and cold. The hives should face the south or south-east, and should be placed on shelves sixty centimeters above the ground, and about the same distance from each other. As to the form of the hives and the materials of which they should be constructed there are great differences of opinion. The old dome-shaped straw skep is still in general use among the cottagers of Great Britain. Its cheapness and simplicity of construction are in its favour, while it is excellent for warmth and ventilation; but it has the disadvantage that its interior is closed to inspection, and the honey can only be got out by stupefying the bees with the smoke of the common puff-ball or chloroform, or by fumigating with sulphur, which entails the destruction of the swarm. Wooden hives of square box-like form gained general favour among bee-keepers from about 1900 onwards. They usually consist of a large breeding chamber below and two sliding removable boxes called supers above for the abstraction of honey without disturbing the contents of the main chamber. It is of great importance that the apiary should be situated in the neighbourhood of good feeding grounds, such as gardens, clover-fields, or heath-covered hills. When their stores of honey are removed the bees must be fed during the winter and part of spring with syrup or with a solution consisting of 1 kg loaf-sugar to about half a litre of of water. In the early spring slow and continuous feeding will stimulate the queen to deposit her eggs, by which means the colony is rapidly strengthened and throws off early swarms. New swarms may make their appearance as early as May and as late as August, but swarming usually takes place in the intervening months. Research Apiary
Bacteria are a diverse group of ubiquitous micro organisms all of which consist of only a single cell that lacks a distinct nuclear membrane and has a cell wall of a unique composition.
Bacteria are usually classified by means of Gram's stain, whether or not they require oxygen, and on the basis of shape. A bacterial cell may be spherical, rod-like, spiral, comma-shaped, corkscrew-shaped, or filamentous, resembling a fungal cell. The majority of bacteria range in size from 0.5 to 5 mm. Many are motile, bearing flagella, possess an outer slimy capsule, and produce resistant spores. In general bacteria reproduce only asexually, by simple division of cells, but a few groups undergo a form of sexual reproduction. Bacteria are largely responsible for decay and decomposition of organic matter, producing a cycling of such chemicals as carbon, oxygen, nitrogen, and sulphur. A few bacteria obtain their food by means of photosynthesis, some are saprophytes, and others are parasites, causing disease. The symptoms of bacterial infections are produced by toxins. Research Bacteria
Abbreviations
Research Chrome Green
